1. Field of the Invention
The present invention relates to a tilt-swivel stand. In particular, it relates to a tilt-swivel stand to support e.g. a CRT (cathode ray tube) for moving the screen of the CRT both in a vertical plane (tilt) and in a horizontal plane (swivel).
2. Description of the Related Art
An example of conventional tilt-swivel stands is disclosed in JP-A-6(1994)-189229. The conventional stand, as shown in FIG. 10 of the accompanying drawings, is provided with a base 50 placed on e.g. a desk, and a movable member 60 upon which a CRT is mounted.
The base 50 is provided at its upper portion with a concave supporting surface 51 coinciding with a part of the surface of a sphere. An upright protrusion 52 extends at the center of the supporting surface 51. The movable member 60 is provided at its lower portion with a convex slide surface 61 whose curvature is equal to that of the above-mentioned concave surface 51. The slide surface 61 is formed with an elongated guide groove 62 to receive the protrusion 52 of the base 50. The width of the groove 62 is slightly greater than the outer diameter of the protrusion 52.
In the assembled state, the concave surface 51 is held in sliding engagement with the convex slide surface 61, with the protrusion 52 extending into the guide groove 62. A screw 70 with a sufficiently large head is driven into the upper portion of the protrusion 52 to prevent the movable member 60 from coming off the base 50.
With the above arrangement, the movable member 60 is still allowed to tilt on the base 50 as the protrusion 52 is moved along the groove 62. Also, the movable member 60 can be swiveled about the protrusion 52 with respect to the base 50, at whatever position the protrusion 30 is located within the guide groove 62.
However, in the conventional tilt-swivel stand, the screw 70 is used for holding the base 50 and the movable member 60 together. Unfavorably, driving the screw 70 into the prescribed portion requires for an additional procedure in the assembly line. Also, to use the screw 70 will raise the production costs.
Another example of conventional tilt-swivel stands is disclosed in JP-A-8(1996)-140017. As shown in FIG. 11 of the accompanying drawings, the conventional stand includes a base (not shown) and a movable member 80 held in sliding engagement with the base, as in the previous conventional stand (FIG. 10). The tilt-swivel stand of FIG. 11 is different from the previous one in that no screw is used for attaching the movable member 80 to the base.
Specifically, as shown in FIG. 11, an upright protrusion 90 is arranged at the center of the base, and a guide groove 81 is formed in the movable member 80 for receiving the upright protrusion 90. The upright protrusion 90 is formed with several fins 90a projecting radially. The guide groove 81 has a uniform width except for one end 81a at which a generally circular through-hole is formed.
For attaching the movable member 80 to the non-illustrated base, the protrusion 90 is inserted into the guide groove 81 at the enlarged end 81a. The end 81a is large enough to allow the fins 90a to go beyond the groove 81. Then, the movable member 80 is caused to slide on the base, so that the fins 90a are moved from the end 81a to the constant-width portion 81b, as shown in FIG. 11. In this state, some of the horizontally projecting pins 90a are caught by the movable member 80, thereby securing the movable member 80 to the non-illustrated base.
With such an arrangement, no additional fixing means such as a screw is needed, which is advantageous to reducing the number of parts necessary for assembling the tilt-swivel stand. Consequently, the production costs and production time are both reduced.
Though the tilt-swivel stand of FIG. 11 has the above advantages, it has been found disadvantageous in the following point.
As long as the protrusion 90 is located in the constant-width portion 81b of the groove 81, the movable member 80 is prevented from coming off the non-illustrated base due to the fins 90a abutting on the movable member 80. However, the protrusion 90 may be brought to the enlarged portion 81a of the groove 81 when the user tilts the CRT mounted on the movable member 80 too much. This unusual positioning of the protrusion 90 relative to the groove 81 is invisible to the user since an CRT is placed on the movable member 80. Thus, unaware of the current situation, the user may try to move the CRT to a different location and lift it. However, with the stopping fins 90a located at the enlarged portion 81a of the groove, the non-illustrated base may come off the movable member 80 and may fall onto the desk.